Well, here's the thing:
This is a "scheme." Not a real job.
The "client" is basically trying to trick you into doing something that will help him, and probably won't help you at all.
Also, this violates Amazon.com ToS.
Which is a problem because Upwork officially states that violating Amazon.com ToS is a violation of Upwork ToS. Think of Amazon.com and Upwork as separate companies which officially are supportive of each other.
Short answer:
This is risky behavior, probably won't lead to earning any money, and you could have your money confiscated or your Upwork profile penalized if you are caught doing this. Furthermore, you could have your Amazon.com account penalized if you are caught doing this.
Now, stepping away from the Amazon.com aspects of this, let's consider another point entirely:
The "client" is asking you to spend your own money upfront, with the "promise" of paying you later. What if he never actually pays you? Then you are left "holding the bag." You didn't earn money. You lost money.
Think about what YOU would do if YOU were hiring a freelancer. If YOU wanted the freelancer to have a book, wouldn't you just send the book to her? Or maybe you would order the book on Amazon.com yourself, with your own money, and have the book shipped to the freelancer. Would YOU ask the freelancer to pay for the book with her own money, or would you send her the book, or at the very least, send her the money up front (via Upwork's expenses or pay bonus tool). You are a professional, ethical person. So you certainly wouldn't ask the freelancer to pay for things without any guarantee that she would actually get paid back later, other than a "promise".
